Two studies are proposed to investigate age differences in self-concept organization across the adult life span, and the extent to which different self-concept organizations are related to affect regulation. These goals are addressed by studying (a) a sample of healthy adults, and (b) a sample of adults who are treated for cancer. The specific aims are: (1) To examine age differences in self-concept organization across the adult life span: Although research with younger age groups has documented the stress-moderating effects of self-complexity (SC) and self-concept differentiation (SCD), knowledge about the adaptive value of these self-concept organizations in adulthood and their relationship with age is limited. Based on findings from earlier work, it is hypothesized that SC will be highest in middle age and lower in young and older adults. Conversely, SCD is hypothesized to be lowest in middle age and higher in young and older adults. (2) To examine the self-regulatory effects of self-representations by modeling daily variation in affect as a function of self-concept organization and daily stress: Self-related knowledge is important for interpersonal functioning and for the regulation of one's own behavior. Building on the existing work in this area, a daily diary study is proposed to examine the self-regulatory functions of self-representations over a 30-day period. Specifically, intra- and inter-individual variability in affect will be modeled as a function of daily stress and SC and SCD. It is hypothesized that SC and SCD will moderate the effects of daily stress on intra- and inter-individual variability in daily affect. (3) To examine the self-regulatory effects of self-representations on affect regulation in adult cancer patients: Being treated for cancer challenges a person's self-concept, self-regulation, and PWB in profound ways. A daily diary study is proposed drawing on 60 men (age 45+) with prostate cancer and 60 women (age 45+) with breast cancer. It is expected that the effect of SC and SCD on affect variability will be significantly stronger in cancer patients than in their healthy counterparts. It is also hypothesized that the moderating effects of SC and SCD on affect variability are significantly (p < .05) greater in the cancer sample than in the healthy sample. The results of these studies will advance the field by providing a more accurate understanding of the role of self-concept organization in affect regulation in healthy and ill adults. This application is submitted under the new investigator provision